1. Field of the Invention
The present invention is broadly concerned with aqueous germicidal iodine/iodide/iodate compositions of very low pH (from about 2-5.5) having enhanced available iodine and free iodine stabilities over extended storage periods of at least about three months. More particularly, the invention pertains to such compositions which contain from about 0.01-1.4% by weight available iodine, from about 10-125 ppm free iodine, from about 0.004-0.50% by weight iodide ion, and from about 0.005-0.5% by weight iodate ion, in combination with an iodine complexing agent. Optional ingredients may include emollients, buffering agents and thickeners.
2. Description of the Prior Art
U.S. Pat. No. 4,271,149 describes aqueous detergent-iodine compositions of the iodine/iodide/iodate variety having pH values of 5-7 with elemental iodine amounts up to about 1% by weight. Typically, representative compositions described within the '149 patent will have free (i.e., uncomplexed) iodine levels of less than 10 ppm. In compositions of this type, two primary competing reactions take place during storage to maintain stability. First, there is some conversion of elemental iodine in the presence of organic matter to iodide ion; second, there is a competing reaction between iodate ion, iodide ion and H.sup.+ to form I.sub.2. Ideally, these two reactions are balanced so that the I.sub.2 content tent of the compositions remains essentially constant.
In recent years, users of germicidal iodine compositions have requested greater and greater amounts of free iodine, e.g., about 20 ppm and above. In order to meet this demand, it is necessary to lower the pH levels of the compositions to achieve these higher free iodine concentrations. However, it was known that at low pH values below 5, the reaction between iodide and iodate to form elemental iodine becomes predominant and can generate excessive amounts of iodine. Hence, products of the type described in the '149 patent, at low pH, would lack requisite long-term stability. Workers in the art have thus faced a heretofore insoluble dilemma: by lowering the pH to achieve and maintain desired higher free iodine levels, the stability of the compositions is very significantly affected, particularly over long storage times.
There is accordingly a real and unsatisfied need in the art for improved aqueous germicidal use compositions of the iodine/iodide/iodate variety which are of very low pH in order to generate/maintain high free iodine levels therein and which are stable over long periods of storage.